Embodiments in accordance with the present invention relate to recording disk drives and to methods of managing defective regions in the same. More particularly, embodiments in accordance with the present invention relate to managing defective regions in a recording disk drive which has a head whose read/write offsets are present.
Devices using various types of media such as optical disks, and magnetic tapes, are known in the art as data storage devices. Among them, hard disk drives (hereinafter referred to as HDD) have become popular as storage devices for computers to such an extent that they are one of the storage devices indispensable for today's computer systems. Further, the HDDs are not limited to use for the computer systems as described above, they are being used in many fields because of excellent characteristics. For example, The HDDs are used for moving picture recording/reproducing devices, car navigation systems, cellular phones, and removable memories for use in digital cameras.
The HDD that writes and reads data using a head element section performs positioning control of a head, based on servo data formed on a magnetic disk. The tracks formed concentrically on the magnetic disk each include a plurality of servo sectors, each of which further consists of servo data and user data. During manufacturing processes of the HDD, servo data is recorded on the magnetic disk by means of a servo-writer or the like.
In recent years, with the tendency to increase the storage capacity and recording density of the HDD, the data track pitches, servo track pitches, and data sector pitches tend to be narrowed. This has been reducing a tolerance for fluctuation of a head element section. The non-uniformity of servo track pitches is produced due to structural non-uniformity of HDDs and the non-uniformity of head positions during servo-writing. The non-uniformity of servo track pitches cannot be ignored while narrowing track pitches or sector pitches.
For example, the non-uniformity of servo track pitches causes the servo tracks to be regionally narrowed. A servo track that is regionally narrowed causes a “squeeze error” in which writing is performed on a track next to a desired track and thus data on the next track is erased. The “squeeze” is an event in which the head element section overwrites a track next to a desired track since a servo track cannot be properly read by a head element section or since a servo track is regionally narrowed or for some other reasons.
Tests for detecting defects on the surfaces of magnetic disks are therefore performed during the manufacturing processes of HDDs. These tests, called SRSTs (Self-Run Self-Tests), are described in Japanese Patent Laid-open No. 2002-260355 (Patent Document 1), for example. In the SRSTs, in addition to SATs (Surface Analysis Tests) for detecting defective regions in which a scratch or the like is formed by performing data read/write operations from/to a magnetic disk, tests called FILL-DATA tests are performed. Defective sectors that have been detected during the tests are registered on a map called PDM (Primary Defect Map). The data sectors that have been registered on PDM are not used.
During the FILL-DATA tests, data is written into all data regions of the magnetic disk and the data tracks on which a write error occurs are detected. All data sectors included in these data tracks are registered on the PDM as defective regions. The FILL-DATA tests are performed to defect the defective regions in which a write error frequently occurs caused by a servo track error such as a servo track narrowed, an unreadable servo track.